Impeller arrangement

ABSTRACT

An impeller arrangement for location for use with a blower and/or vac device, the impeller being rotatable about an axis of rotation and comprising a base, a shroud and a plurality of blades located therebetween, the shroud comprising an impeller inlet defining a passageway to the plurality of blades, a barrier arrangement located adjacent the impeller inlet to restrict airflow between the impeller and its housing. By providing such an arrangement, inlet losses to the impeller can be reduced when compared to known arrangements. The interaction between these components forms a barrier to bleeding of the airflow away from the inlet, reducing the likelihood of air passing between the impeller and its housing and improving the inlet efficiency of the impeller.

TECHNICAL FIELD

The present invention relates to an impeller arrangement. Moreparticularly, an impeller arrangement for blower vacuums, vacuums and/orblower appliances.

In general, blower vacuum appliances comprise a motor and fanarrangement. The motor is usually either petrol or electrically powered.The fan comprises a centrifugal impeller enclosed within a toroidalenclosure known as a volute. The impeller is configured, in use, to drawair in along the axis of rotation towards the centre or “eye” of theimpeller and expel air out radially. The volute comprises a fluid inletsurrounding the eye of the impeller and aligned with the axis ofrotation of the impeller, and a fluid outlet located at a point on theperiphery of the volute. The shape of the volute essentially directs theradially-moving air towards the fluid outlet.

Blower vacuum appliances generally have two modes of operation: blowingand vacuuming. In the blowing mode, clean air is drawn into the volutefrom the atmosphere via the fluid inlet and is expelled via the fluidoutlet. A blower tube is attached to the outlet in order to focus anddirect the expelled air into a jet. This jet of air may be aimed throughmanipulation of the blower tube or blower vacuum to move or gathergarden waste.

When in the vacuuming mode, garden waste may be collected up a suctiontube connected to the blower vacuum. There are two common structuralarrangements for a blower vacuum appliance having a vacuum mode: dirtyfan and clean fan configurations.

In a dirty fan arrangement, a suction tube having a suction inlet isconnected to the fluid inlet of the volute and a debris collector (whichmay comprise separation means such as a semi-porous bag or container)for garden waste is attached in direct fluid connection to the fluidoutlet of the volute. Therefore, in this arrangement, the fan is locateddirectly in the flowpath from the suction inlet to the debris collector.Consequently, garden waste or debris entrained in the air passing intothe suction inlet passes through the fluid inlet of the volute andcollides with the fan before being passed via the fluid outlet of thevolute into the debris collector. This arrangement enables garden wasteor debris to be broken down or mulched into smaller particles forefficient collection in the debris collector.

In a clean fan arrangement, a debris collector (which may compriseseparation means such as a semi-porous bag or container) for gardenwaste is also attached in direct fluid connection to the fluid outlet ofthe volute. However, in contrast, a suction tube comprising a suctioninlet is connected downstream of the fluid outlet of the volute.

Therefore, in the same manner as for the blowing mode, in use, air isdrawn into the fluid inlet of the volute from the atmosphere andexpelled from the volute through the fluid outlet towards the debriscollector. The flow of air from the fluid outlet and into and throughthe debris collector causes a pressure differential between the proximaland distal ends of the suction tube. This causes air to be drawn intothe suction inlet, through the suction tube and into the debriscollector. Consequently, any garden waste or debris entrained in the airpassing into the suction tube will be deposited into the debriscollector.

This arrangement has the advantage that the fan is supplied with a cleanstream of air at all times and so can operate under optimal conditionswith relatively little chance of blockages forming.

An alternative arrangement is simply a blower appliance without a vacuumfunction. This arrangement operates in the same manner as the blowermode of the clean fan arrangement. Clean air is drawn into a volute fromthe atmosphere via a fluid inlet and is expelled via a fluid outlet. Ablower tube attached to the fluid outlet focuses and directs theexpelled air into a jet. This jet of air may be aimed throughmanipulation of the blower tube or blower vacuum to move or gathergarden waste.

Blower vacuum and/or blower appliances are often required to generatehigh flow rates of air through the impeller to produce a powerful jet ofair (in the blower mode) or powerful suction (in the vacuum mode, whereappropriate) in order to clear an external environment of debris andwaste. Therefore, it is beneficial to minimise losses in the appliancein order to maximise the available airflow.

Commonly, in a volute arrangement comprising a centrifugal impeller, airis directed towards the eye of the impeller and is then directedradially outward therefrom. However, due to the pressure distributionthus created, some of the air passing into the volute inlet may not passaxially directly into the impeller and may, instead, pass substantiallyradially between the volute housing and the upper surface of theimpeller (known as a shroud). This airflow essentially bypasses theimpeller and, consequently, is not accelerated thereby. This may reducethe inlet efficiency of the impeller because not all of the air admittedthrough the volute inlet passes through the impeller.

As a result, there is a need in the art to provide an impellerarrangement which has lower losses than known arrangements.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is providedan impeller arrangement for location in an impeller housing delimiting ahousing inlet, the impeller being rotatable about an axis of rotationand comprising a base, a shroud and a plurality of blades locatedtherebetween, the shroud comprising an impeller inlet defining apassageway extending to the plurality of blades, wherein the impellerarrangement further comprises a barrier arrangement located adjacent theimpeller inlet and arranged to receive, or extend into, a portion of theimpeller housing surrounding the housing inlet to restrict airflowbetween the impeller housing and the shroud.

By providing such an arrangement, inlet losses to the impeller can bereduced when compared to known arrangements. A barrier arrangementprovided on the shroud of an impeller is located in close relationshipwith a complementary portion of the impeller housing adjacent the airinlet. The interaction between these components forms a barrier tobleeding of the airflow away from the inlet, reducing the likelihood ofair passing between the shroud and the impeller housing and improvingthe inlet efficiency of the impeller.

In one embodiment, the barrier arrangement and said portion of theimpeller housing define a convoluted path therebetween. By defining aconvoluted or labyrinthine pathway between the shroud and the impellerhousing, the airflow is forced to undergo numerous directional changes,resulting in a reduction in airflow bleeding and reduced flow rate.

In one embodiment, the barrier arrangement comprises an annular channelarranged to receive a portion of the impeller housing therein. Thisarrangement provides a straightforward and reliable method for providinga barrier to airflow bleeding.

In one embodiment, the barrier arrangement comprises two radially-spacedannular ribs formed on the shroud and defining the channel therebetween.Ribs are straightforward to form during manufacture and provide thenecessary barrier properties.

In one embodiment, the barrier arrangement surrounds the impeller inlet.By surrounding the impeller inlet with the barrier arrangement, thechance of air bleeding away from the impeller inlet is reduced.

According to a second aspect of the present invention, there is provideda fan arrangement comprising: an impeller housing delimiting a housinginlet; and an impeller arrangement according to the first aspect.

In an embodiment, an annular housing rib is located on the periphery ofthe housing inlet and is arranged to be located within the annularchannel. This provides a reliable and easy to locate structuralrelationship to form a convoluted physical path to mitigate a leakageairflow.

In one embodiment, the annular housing rib is spaced from the base andsides of the annular channel. This provides sufficient tolerance toprevent contact between the housing rib and the shroud of the impellerduring use.

In one embodiment, the impeller housing comprises a volute.

In one embodiment, the volute comprises a scroll-type volute outletdownstream of the impeller. A scroll-type volute is particularly usefulfor directing and channelling airflow downstream of the impeller.

According to a third aspect of the present invention, there is providedan appliance comprising the fan arrangement of the second aspect.

In one embodiment, the appliance is in the form of a debris blowerand/or vacuum appliance.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings, in which:

FIG. 1 is a side view showing the general configuration of a blowerappliance;

FIG. 2 is a side view showing the general configuration of a blowervacuum appliance;

FIG. 3 is a cross sectional view of a volute according to an embodimentof the present invention;

FIG. 4 is a sectional plan view of the volute of FIG. 3;

FIG. 5 is a perspective view of part of the volute of FIG. 3;

FIG. 6 is a perspective view of an impeller according to an embodimentof the present invention;

FIG. 7 is a perspective view showing the impeller of FIG. 6 located in apart of the volute of FIG. 3; and

FIG. 8 is a detailed cross sectional view of a part of the volute ofFIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an impeller and volute arrangement whichreduces inlet losses to the impeller when compared to knownarrangements. A barrier arrangement provided on the shroud of animpeller is located in close relationship with a complementary portionof the volute adjacent the air inlet.

The interaction between these components defines a convoluted orlabyrinthine pathway between the shroud and the volute housing, reducingthe likelihood of air passing there between and improving the flow ofair into the eye of the impeller.

The general configuration of a blower appliance and a blower vacuumappliance will now be described with reference to FIGS. 1 and 2.

FIG. 1 shows an example of a blower (or sweeper) appliance 10 in whichembodiments of the present invention may be used. The blower appliance10 is an electrically-powered appliance which comprises a battery pack.However, alternatively the blower appliance 10 may be mains-powered orcomprise an internal combustion engine and fuel tank.

The blower appliance 10 comprises a body 12 which may be formed from ahardened plastic material. The body 12 comprises a volute 14 and agraspable handle 16. A removable power source 18 (in the form of abattery pack) is located at the base of the handle 16.

The volute 14 is essentially disc shaped and houses a motor and impellerarrangement (not shown in FIG. 1) for generating an airflow through theblower appliance 10. The volute 14 comprises an air inlet 20 located atthe centre of the disc-shaped volute 14 and an air outlet 22 extendingtangentially away from the disc shaped portion of the volute 14.

The impeller is operable to draw an airflow through the air inlet 20 andexhaust the airflow through the air outlet 22. The air inlet 20, asshown, is covered by a grille or cover 24 which prevents a usercontacting rotating parts located therein. The spacing of the grille 24is such to prevent insertion of a human finger according to existingsafety standards.

A detachable blower tube 26 is connected to the air outlet 22 andcomprises an exhaust outlet 28 at a distal end thereof. The blower tube26 narrows from the adjacent the air outlet 22 to the exhaust outlet 28to focus and direct the airflow into a powerful jet.

A blower vacuum appliance 30 is shown in FIG. 2 in which embodiments ofthe present invention may be used. The blower vacuum appliance 30 issimilar in configuration to the blower appliance 10 of FIG. 1 and is anelectrically-powered appliance which comprises a battery pack.

The blower vacuum appliance 30 comprises a body 32 comprising a volute34 and a graspable handle 36. A removable power source 38 (in the formof a battery pack) is located at the base of the handle 36.

The volute 14 is essentially the same as that of the blower appliance 10and houses a motor and impeller arrangement (not shown in FIG. 2) forgenerating an airflow through the blower vacuum appliance 30. However,in this instance, the blower vacuum appliance 30 is a dirty-fanarrangement and so the impeller is configured to receive debris andmulch the debris.

The volute 34 comprises an air inlet 40 located at the centre of thedisc-shaped volute 34 and an air outlet 42 extending tangentially awayfrom the disc shaped portion of the volute 34. In this arrangement, asuction tube 44 is connected to the air inlet 40 and comprises a suctioninlet 46 at a distal end thereof. The suction tube 44 is configured todraw air and entrained debris through the suction inlet 46 and into thevolute 34 where the debris is mulched.

A debris collector 48 is connected directly to the air outlet 42 andprovides a collection receptacle for the mulched debris passed throughthe volute 34. The debris collector 48 is semi-porous so that air canescape therethrough and may comprise, for example, a nylon bag or othercollection means.

The blower vacuum appliance 30 as described above is shown in a vacuummode of operation. In order to operate in a blower mode, the suctiontube 44 can be detached and connected to the air outlet 42 in the mannerof the blower appliance 10. A grille (not shown) can then be connectedto the air inlet.

FIGS. 3 to 7 shows a section through a volute assembly 100 according toan embodiment of the invention. Referring to FIGS. 3 to 6, the voluteassembly 100 comprises first and second clamshell portions 102, 104. Theclamshell portions 102, 104 define a central hub 106 and a scrollportion 108 located outwardly of the hub 106.

The hub 106 comprises an air inlet 110 located centrally at an upperportion thereof. The air inlet 110 is covered by a grille 112. Animpeller 200 is located at the centre of the hub 106 in communicationwith the air inlet 110. The impeller 200 is mounted on a drive shaft 202connected to a motor 204. The impeller 200, in use, is operable torotate on the drive shaft 202 about an axis X-X which is coincident withthe centre of the hub 106.

A diffuser 114 is located radially outwardly, and downstream, of theimpeller 200 and comprises an annular channel delimited by two diffuserwalls 116, 118. The diffuser 114 is located between the hub 106 and thescroll portion 108 of the volute 100 and has a narrower height thaneither the hub 106 or the scroll region 108.

The diffuser 114 is vaneless. That is to say no vanes, projections orguides are located in the annular channel comprising the diffuser 114and the diffuser 114 essentially comprises an annular channel defined bythe two planar, spaced apart annular walls 116, 118. The diffuser 114 issymmetrical about the axis X-X and has a constant height and width.

The scroll portion 108 is located in the flowpath immediately downstreamof the diffuser 114. The scroll portion 108 comprises a spiral,scroll-like cavity 120 defined by volute walls 122. The volute walls 122have a circular cross section which increases in diameter in ananticlockwise direction (as shown in FIG. 4) from a position adjacent avolute tongue 124 located adjacent the outer portion of the diffuser 114to terminate in an air outlet 126.

The air outlet 126 is formed at a distal end of a tangential section 128of the scroll portion 108. As shown in FIG. 4, the volute tongue 124delimits a portion of the tangential section 128 leading to the airoutlet 126.

The impeller 200 will now be described in detail with reference to FIGS.6 to 8. In FIG. 6, the impeller 200 is shown removed from the volutearrangement 100. In FIG. 7, the impeller 200 is shown located on thelower clamshell portion 104 with the upper clamshell portion 102removed.

The impeller 200 includes a base 206, a shroud 208 and a plurality offan blades 210 located therebetween. The base 206 extends radially fromthe axis X-X of the drive shaft 202 parallel to the diffuser 114. Thefan blades 210 extend perpendicularly from the base 206 and are curvedfor aerodynamic efficiency. The shroud 208 delimits an axially-arrangedinlet 212 to the eye of the impeller 200. When fitted in the volute 100,the inlet 212 to the impeller 200 is co-axial with, and locatedadjacent, the air inlet 110 formed in the hub 106 of the volute 100.

The shroud 208 comprises a barrier arrangement 214 located on a surfacethereof facing away from the base 206. The barrier arrangement 214comprises two annular ribs 216, 218 which project away from the shroud208 and surround the inlet 212. The innermost annular rib 216 forms apart of the boundary wall delimiting the inlet 212.

The annular ribs 216, 218 define an annular channel 220 therebetween.This is shown in FIG. 8. FIG. 8 shows a cross-sectional view (similar toFIG. 3) through the volute 100 showing the impeller located in the hub106 of the volute 100.

As shown in FIG. 8, a complementary annular volute rib 130 is formed onthe inner surface of the wall of the hub 106 of the volute 100. Theannular volute rib 130 extends into the annular channel 220 formed bythe annular ribs 216, 218, defining a convoluted or labyrinthine path P(FIG. 8) from the air inlet 110 through the annular channel 220.

The volute rib 130 is spaced from the annular ribs 216, 218 in bothaxial and radial directions to ensure that, in use, tolerances aresufficient to prevent contact between the volute rib 130 and the annularribs 216, 218 (which will be rotating with the impeller 200).

As shown in FIG. 8, an internal inlet wall 132 of the inlet 110 islocated at the same radial spacing as the inner annular wall 216 todefine an essentially smooth (with the exception of the necessary axialspacing between the annular wall 216 and the internal inlet wall 132)inlet flowpath for air entering the inlet 110 and passing through theinlet 212 into the eye of the impeller 200.

In use, when the motor 204 is activated by a user, the drive shaft 202will be caused to rotate. The impeller 200, which is secured to thedrive shaft 202, will also be caused to be rotated. Thus, an airflow isdrawn in through the volute inlet 110 and through the inlet 212 of theimpeller 200. The air is then guided onto the fan blades 210 where it isaccelerated and dispersed radially outwardly by the fan blades 210. Thiscauses a pressure drop across the impeller 200 because the airdownstream of the impeller 200 is moving faster than the upstreamairflow. This, in turn, causes further air to be drawn into the voluteinlet 110 and into the impeller 200.

In conventional centrifugal impeller arrangements, the pressure dropacross the impeller may cause unwanted bleeding of air around the edgesof the impeller inlet and between the volute housing and impellershroud. This reduces throughput of air onto the impeller and theefficiency of the impeller.

However, in the above-described embodiment, the location of the voluterib 130 in the annular channel 220 formed by the annular walls 216, 218forms a barrier to reduce bleeding of inlet air in this manner. Theclosely-spaced relationship of the volute rib 130 and annular walls 216,218 forms the labyrinthine pathway P between the inlet 110 and theoutlet of the impeller 200.

Thus, in order to pass through the labyrinthine pathway P, the air isforced to follow a convoluted path having a plurality of directionchanges. Each direction change will bleed energy from the airflow andwill cause stagnation points at each direction change point. This, inturn, reduces the speed of the airflow therethrough and, consequently,the volume of air flowing per unit time between the volute housing 102and the shroud 208 of the impeller 200.

As a result, the leakage of air is reduced, enabling more airflowpassing through the volute inlet 110 to pass directly into inlet 212 ofthe impeller 200. This improves the airflow impinging upon the fanblades 210, ensuring that the impeller 200 can operate at a highefficiency. The airflow then passes through the fan blades 210, acrossthe diffuser 114 and is exhausted into the scroll portion 108 of thevolute 100. The airflow is then directed around the volute walls 122towards the tangential portion 128 and through the air outlet 126.

Variations of the above embodiments will be apparent to the skilledperson. The precise configuration of components may differ and stillfall within the scope of the present invention.

For example, while the above example has been described with referenceto blower or blower vacuum appliances generally for use in a domesticenvironment, the invention is readily applicable to other machinescomprising centrifugal impellers. For example, embodiments of thepresent invention are equally applicable to a domestic or industrialvacuum cleaner. Additionally or alternatively, the inlet efficiency ofany arrangement comprising a centrifugal fan or impeller could beimproved by the present invention. Non-exhaustive examples of this mayinclude turbochargers or centrifugal pumps. Indeed, a volute need not beprovided and any suitable impeller housing may be used.

While the barrier arrangement of the above example has been described ascomprising a pair of annular ribs defining a channel into which a voluterib is received, this need not be the case. The skilled person would bereadily aware of variations and modification which will fall within thescope of the present invention. For example, the barrier arrangement maycomprise an annular channel formed as a recess in the inlet-facingsurface of the shroud without the need for projecting ribs.

Alternatively, the channel may be formed in the inner surface of thevolute wall and a single projecting rib may be provided on the shroud toextend into the channel formed in the volute wall. This may comprise twoor more spaced ribs on the volute housing or the channel may be formedas a recess in the volute housing.

In general, the barrier arrangement may comprise any suitablearrangement which forms a barrier to restrict flow of air between theimpeller shroud and the volute housing. This may involve providingmembers located on the impeller which overlap with members located onthe volute housing when viewed in a radial direction. This is so thatair passing between the volute housing and the shroud is forced tofollow a convoluted path with at least one direction change.

Further, while the above embodiment has been shown and described withreference to an axially-extending barrier arrangement, radiallyextending barrier arrangements could be utilised. For example, anannular rib may comprise a radially extending flange that projects intoa recess formed in the side wall of the volute inlet.

While a barrier arrangement comprising a single channel with a singleprojecting rib extending therein have been shown and described, thebarrier arrangement may comprise any number of channels and/or ribs orvariations as discussed above.

Embodiments of the present invention have been described with particularreference to the examples illustrated. While specific examples are shownin the drawings and are herein described in detail, it should beunderstood, however, that the drawings and detailed description are notintended to limit the invention to the particular form disclosed. Itwill be appreciated that variations and modifications may be made to theexamples described within the scope of the present invention.

1. An impeller arrangement comprising an impeller located in a volute ofa device, the impeller being rotatable about an axis of rotation andcomprising a base, a shroud and a plurality of blades locatedtherebetween, the shroud comprising an impeller inlet defining apassageway to the plurality of blades, wherein the impeller interactswith a portion of the volute surrounding the impeller inlet to form abarrier arrangement located adjacent the impeller inlet to restrictairflow between the volute and the shroud.
 2. The impeller arrangementaccording to claim 1, wherein the barrier arrangement forms a convolutedair path.
 3. The impeller arrangement according to claim 2, wherein thebarrier arrangement comprises the shroud forming an annular channelwhich receives a portion of the volute therein.
 4. The impellerarrangement according to claim 3, wherein the shroud comprises twoparallel spaced ribs defining the channel therebetween.
 5. The impellerarrangement according to claim 4, wherein the volute includes a rib thatis located within the channel formed by the shroud to form theconvoluted air path.
 6. The impeller arrangement according to claim 5,wherein the volute comprises a scroll-type volute outlet downstream ofthe impeller.
 7. An impeller for a blower device, the impeller beingsecured to a drive shaft of a motor and rotatable about an axis ofrotation, the impeller comprising a base, a shroud and a plurality ofblades located therebetween, the shroud comprising an impeller inletdefining a passageway to the plurality of blades; wherein the impellerinteracts with a portion of the volute surrounding the impeller inlet toform a barrier arrangement located adjacent the impeller inlet torestrict airflow between the volute and the shroud.
 8. The impelleraccording to claim 7, wherein the shroud includes a pair of parallelribs that interact with a rib on the volute to form the barrierarrangement.